This invention relates to a photoelectric sensing array system, method and apparatus for a touch input device or touch screen. Touch screens are often used in conjunction with a display as an input device to a computer display, a kiosk display, or other display application. The touch screen device is typically a finger as shown in FIG. 1. Other touch means may be employed such as a pointer, pencil, or other object.
There are different types of touch screens available including infrared, resistive, capacitive, and acoustic wave. This invention relates to infrared touch screens. Infrared touch screens comprise an array of infrared photo emitters, each paired with an array of infrared (IR) photo detectors.
The position of an opaque object located between the transmitting array and the receiving array is determined by individually pulsing the infrared photo emitter sources while electronically sensing the response of the corresponding photo detectors.
The IR prior art discloses arrays that produce a multitude of invisible light beams, whereby corresponding sensors are blocked at the position where an opaque object is located. The center of the opaque object can be determined by electronically sensing current flow in each of the photo sensors, and then computing the center point of the region of blocked photosensors. Commonly this IR detection process is done in two axes simultaneously to create a two dimensional sensing grid such as found on a computer touch screen as shown in FIG. 1.
In the IR prior art, the sensor arrays of this type have the light emitting transmitters mounted on one side and the photo detecting receivers mounted on the opposite side. See U.S. Pat. Nos. 4,672,364 (Lucas); 4,841,141 (Ouchi); 4,891,508 (Campbell); 4,893,120 (Doering et al); 4,904,857 (Ando et al); 4,928,094 (smith); 5,162,783 (Moreno) and 5,579,035 (Beiswenger), which are each incorporated herein by reference.
Technical and manufacturing improvements in the production of displays such as LCD, plasma, and rear projection have made available large area displays. Large displays are desirable in applications such as dynamic signage, kiosks, lobby portholes, and games. These large displays require large touch screens to provide a large interactive display surface.
The development and production of large touch screens is complex. Resistive and capacitive touch screens are not easy to fabricate in large sizes due to poor yield. Similarly, acoustic wave attenuates with large touch systems size. Infrared touch screens are more readily scaled to large sizes than other touch system technologies. However, problems such as alignment of sensors, resolution, mean time between failures and manufacturability are magnified with increasing size.